Gyroscopic compass



Patented Apr. 16, 1929.

UNITED STATES PATENT oFPicE.

i REGINALD E. GILLMOR, OF STMFORD, CONNECTICUT, ASSIGNOR, BY MESNE ASSIGN;

MENTS, TO SPERRY GYROSCOPE COMPANY, INC., OF BROOKLYN, YORK, A COR- PORATION 0F NEW YORK.

GYRosecPIo COMPASS.

Application filed February 4, 1926.v Seriall No. 85,927.

This invention relates to refinements in gyroscopic compasses dealing With the variations in the behavior of the compass due vto changing latitudes. It has long been recognized that for the best results the pendulous factor of the gyroscope should be so related tothe other factors that on change in speed or coarse of the ship the compass will be brought to its new settling point by the direct action of the acceleration pressure on the gravitational factor so that no oscillations are set up therefrom. This action of the acceleration forces on the compass produces What is known as the ballistic .deflection. The permanent change in'setthng point of the compass for changes in speed and course is usually referred to as the speed and course error, andthe aim of the compass engineer should be to make these factors equal. The speed and course error is corrected for in the Sperry compass by .the

correction device correcting the readings ofthe compass in accordance With the speed, course and latitude.

It has been found, however, since the speed and course error varies With the latitude, that a pendulous factor of the compass which is designed for a particular latitude, Will not give the compass quite the proper ballistic deflection for other latitudes to prevent the setting up of oscillations if the other factors, suchras the rotor speed, remain constant. Heretfore itl has been the practice to design Compasses so that theballistic deflection is correct for a single mean latitude, leaving a residual uncorrected error for all other latitudes. Also, it is recognized that in the prior patent to I'Iarrisonl and Rawlings- #1,362,940, vgyroscopic Compasses, December 21, 1920, assigned to the assignees of the present. application, means are provided for minimizing this defect to some extent by providing a plurality of gravitational fi'ictors which may be used selectively or in combination. In the present invention, however, greater accuracy is secured by providing means for varying the pendulous factor at Will and through any desired num'- ber of small chan es so that the magnitude of the pendulous actor may be as carefully adjusted as any .other feature of the comass. p Referring to the drawingsVl in which what is now considered the preferred form of ythe invention is shown Fig. 1 is an end elevation, partly in section, of a gyro compass of the Sperry liquid control type' With my invention applied thereto.

Fig. 2v is a longitudinal section ona large scale of one of the liquid containers forming', together with the liquid therein, the gravitational factor.

Fig. 3 is a side elevation on a still larger scale ofthe liquid container showing the ad'- justing means for the same.

Vhile my invention is shown as applied particularly to the Sperry type liquid controlled compass, it Willv be obvious that the principles therein may be utilized in other types of Compasses Within the spirit and scope of the appended claims. The Sperry type compass, howeveigis especially adapted for my inventionsince the gravitational element therein also applies a damping couple so that When the gravitational factor is varied the damping factor is automatically varied in the same proportion and thereby the percentage damping remains undisturbed. y

The compass in Fig. l is shown as having the usual gimbal support 1, for the spider 2 from` Which the compass is sus pended, the usual follow-up or phantom rin g 'being shown at 3, the vertical ring at 4 and iliade slightly Aeccentric for damping purposes, but damping may obviously be secured by other means, as Amy invention does not rclate to damping.' The liquid 14, such as-mercury, Within the boxes, acts as the gravitational factor of the compass. The value or magnitude of the liquid gravitational factor, such as liquid 14, depends primaril on three factors, first, the density or speci c gravity of the'liquid, second, on the area of the eifposed surface l` of the saule, whichis in communication with thev transfer pipe l2,

and third, on the lever arm through which 1t acts, or m other words, the dlstance of the center of gravity of the liquid horizonthe area of what may be termed the working portion or effective area of the liquid. To effect this I provide within each of the boxes 11 a sliding piston 16 with suitable means for adjusting it at will. To this end I may provide the piston with a threaded aperture 17 in which is threaded a rotatable stem or rod 18. Said rod is journaled at one end in a bracket 19 extending across the box and at. the other -end in the sleeve or bushing l20. To rotate said rod I provide .a knurled knob 21 so that the piston may be readily adjusted to any position in the box shown by the dotted line positions 22 and-23. The

. piston, it will be seen, divides the box into two compartments, the relative size of which maybe varied at will and only one of which, namely the right hand compartment in Fig.

2, is in communication with the pipe 12 so that the area of the liquid in this compartment may be varied at will.

JIn order, however, to prevent a change in the height of the liquid,vdue to movements of he piston and consequent change `in the balance of the compass, I provide a by-pass through or around the piston. This may-be ,provided by boring a small hole .24 through the rod 18 which has a laterally extending passage 25 connected thereto adja- -cent4 thefouterend. A small needle valve 26 is shown for closing and opening said passage 25 atwill, said needlevalve'liaving a'threaded stem 27 and being rotated by knurled knob 28.

- It is also desirable that indicating means be provided, graduated to indicate latitude to show where the piston should be placed for different latitudes. For this purpose I have shown a second rod 28 provided with a very coarse spiral thread 29 making valve 26 by -turning the knobV 28, then the knob 21 isi-.turned until the indicator is brou ht to thel roper latitude reading after whic the nee e valve 26 is again closed. By this procedure the effective area of the inerruryis varied at will while permitting at all times an equal amount on both sides of the piston to maintain the compass balance. It will also be readily seen that since the damping is applied through the eccentric connection 13, that any variation in the effective arca of the mercury, resulting in the variation in the gravitational torque, would also effect a corresponding change in the damping torque, vsince b oth torques are really but a single torque about an inclined axis at right angles to the eccentric connection.

In accordance with the provisions of the lpatent statutes, I have herein described the principle and operation of my invention, together with theapparatus which I know consider to represent the best embodiment thereof,but I desire to have it understood that the apparatus shownis only illustrative and thatthe invention can be carried out by other means. Also, While it is designed to usey the various features and elements in the combination and relatlons described, some of these may be altered and others omitted without interfering with `the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Pat-ent 1. In a liquid controlled gyro-compass, the combination with the liquid containers, of a. piston slidably mounted therein to var the effective liquid surface, means for a esv justing the same, means forming a by-pass permitting the flow of liquid around said piston, and a valve for closing the same.

" 2. In a gyro-compass, having a pendulous factor, rotatable means for varying the gravitation moment o f said factor through small increments, and a latitude scale adjustable -with said means whereby the value of said moment' maybe varied according tothe latitude.

3. In aliquid controlled gym-compass, the'.

combination with the liquid containers, of

a piston slidably mounted therein to vary the effectivel liquid surface, means for adjusting the same, and a latitude scale cooperating therewith.

4. In a liquid controlled gyro-compass, the combination with the liquid containers, of a 'piston slidably mounted therein to vary the effective liquid surface, means for adjusting the same, a latitude scale cooperating therewith, a by-pass permitting the flow of liquid around said piston,and` a valve for closing the same independently of the action of said adjusting'means. l

5. Ina liquid controlled gyro-compa'ss, the combination with the liquid containers, of a piston slidably mounted therein to vary the effectiveli uid surface, a threaded rod for adjusting t 1e same, a second threaded rod of larger pitch and adaptedito be rotated by movement of said piston, and a latitude scale rotated by said first and second rods respectively.

6. In a liquid controlled gym-compass, the combination with the liquid containers, of a piston slidably mounted therein to vary the efective liquid surface, a threadedrod for adjusting the same, a by-passbore through said rod opening on both sides of said piston, and a valve for closing said bore.

7. In a gyroscopic compass, the combination with a gravitational factor which also applies the damping factor, of-means for varying the former through small increments whereby the vlatter is also varied proportionately, and a latitude scale adjustable with said means whereby both the gravitational and damping factors may be varied according to the latitude.

In testimony whereof I have affixed my signature.

REGINALD E. GILLMOR. 

